Recently, studies and researches have been actively carried out with respect to a MIMO (Multiple Input Multiple Output) system.
MIMO technologies are classified into diversity and multiplexing technologies. The diversity technology includes a STC (Space-Time coding) technology configured to obtain a space-time diversity gain by using multiple transceive antennas. The multiplexing technology includes a BLAST (Bell-Lab Layered Space-Time) technology to transmit different data to each transmit antenna. In addition, recently, a D-STTD (Double-Space Time Transmit Diversity) technology has been developed to obtain both effects of the diversity and multiplexing technologies.
The D-STTD technology is the combination of spatial multiplexing and STTD technologies, and employs two STBCs (Space-Time Block Codes) for a pair of antennas. According to the D-STTD technology, after forming two symbol sequences through spatial multiplexing, a pair of antennas are allocated to each symbol sequence and then the STTD scheme is applied. Therefore, in order to apply the spatial multiplexing and the STTD technologies, the total four transmit antennas are required, and at least two receive antennas are required to detect spatial-multiplexed symbols. In the D-STTD technology, since four symbols are transmitted for the duration of two symbols, the throughput the same as that of the spatial multiplexing technology employing two transmit antennas can be obtained. In addition, since two pairs of antennas are used in the STTD technology, the transmission diversity gain the same as that of the conventional STTD can be obtained.
Therefore, various methods to enhance data transmission/reception efficiency are required in a system with the D-STTD technology.